NED Abstract

Copyright by European Southern Observatory (ESO).
Reproduced by permission
1996A&A...315...40S
CCD photometry of the Tucana dwarf galaxy.
Saviane I., Held E.V., Piotto G.
Dipartimento di Astronomia, Universita di Padova, vicolo
dell'Osservatorio 5, I-35122 Padova, Italy
Osservatorio Astronomico di Bologna, Via Zamboni 33, I-40126 Bologna,
Italy
Received 30 January 1996/Accepted 9 April 1996
Abstract. We present V and I CCD photometry for ~360 stars in the
recently discovered dwarf galaxy Tucana. The large field investigated and
the accurate photometric calibration make our data complementary to the
deeper HST photometry. From the I magnitude of the tip of the red giant
branch we estimate a distance modulus (m-M)_0_ = 24.69+/-0.16,
corresponding to 870+/-60Kpc, confirming that Tucana is an isolated dwarf
spheroidal located almost at the border of the Local Group. From the
color of the red giant branch tip and by direct comparison with the giant
branches of galactic globular clusters we estimate a metallicity [Fe/H]=-
1.810.2, with no clear indication for a metallicity spread. The color-
magnitude diagram indicates that Tucana has had a single star formation
burst at the epoch of the Galactic globular cluster star formation. There
is no evidence for an intermediate or young stellar population. We derive
the V luminosity profile, the surface density profile of resolved stars,
and the structural parameters of Tucana, from which we confirm that
Tucana participates to the general metallicity-surface brightness-
absolute magnitude relations defined by the Galaxy and M31 dwarf
spheroidal and dwarf elliptical companions.
Keywords: galaxies: fundamental parameters - galaxies: individual: Tucana
- Local Group - galaxies: stellar content - galaxies: structure